Compact efficient hydrogen reactor

ABSTRACT

Methods and devices and aspects thereof for generating power using PEM fuel cell power systems comprising a rotary bed (or rotatable) reactor for hydrogen generation are disclosed. Hydrogen is generated by the hydrolysis of fuels such as lithium aluminum hydride and mixtures thereof. Water required for hydrolysis may be captured from the fuel cell exhaust. Water is preferably fed to the reactor in the form of a mist generated by an atomizer. An exemplary 750 We-h, 400 We PEM fuel cell power system may be characterized by a specific energy of about 550 We-h/kg and a specific power of about 290 We/kg. Turbidity fixtures within the reactor increase turbidity of fuel pellets within the reactor and improve the energy density of the system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of International Patent ApplicationNo. PCT/US2018/049561 filed Sep. 5, 2018, which claims the benefit ofU.S. Provisional Patent Application No. 62/554,495 filed Sep. 5, 2017,the entire contents of which are incorporated by reference herein.

FIELD

The present disclosure relates to methods and devices for PEM fuel cellpower systems with efficient hydrogen generation. In particular, itrelates to using rotary bed reactors to generate hydrogen required forthe operation of PEM fuel cell power systems by the hydrolysis of fuels.

BACKGROUND

Fuel cells are electrochemical energy conversion devices that convert anexternal source fuel to electrical current. If any fuel cells usehydrogen as the fuel and oxygen (typically from air) as an oxidant. Theby-product for such a fuel cell is water, making the fuel cell a verylow environmental impact device for generating power. For an increasingnumber of applications, fuel cells are more efficient than conventionalpower generation, such as combustion of fossil fuel, as well as portablepower storage, such as lithium-ion batteries.

A fuel cell provides a direct current (DC) voltage that can be used fornumerous applications including stationary power generation, lighting,back-up power, consumer electronics, personal mobility devices, such aselectric bicycles, as well as landscaping equipment and otherapplications. There are a wide variety of fuel cells available, eachusing a different chemistry to generate power. Fuel cells are usuallyclassified according to their operating temperature and the type ofelectrolyte system that they utilize. One common fuel cell is thepolymer exchange membrane fuel cell (PEMFC), which uses hydrogen as thefuel and oxygen (usually air) as its oxidant. It has a high powerdensity and a low operating temperature of usually below 80° C. Thesefuel cells are reliable with modest packaging and system implementationrequirements.

In a PEMFC, hydrogen gas is fed to the anode side, ionizes and releasesprotons as follows:2H₂→4H⁺+4e ⁻

The protons pass through the electrolyte to the cathode side while theelectrons are conducted through an external electrical circuit to thecathode side. At the cathode side, oxygen (usually from ambient air)reacts with the electrons and the protons to form water as follows:O₂+4e ⁻+4H⁺2H₂O

Water produced at the cathode is generally exhausted out to the ambientor condensed and used to cool the PEMFC. The production of water howeveroffers an opportunity to harvest the product water and use some or allof it to generate hydrogen by hydrolysis with chemical hydrides.

The requirement of high purity hydrogen, hydrogen storage and/orgeneration has limited the wide-scale adoption of PEM fuel cells(PEMFC). Although molecular hydrogen (e.g. compressed hydrogen) has avery high energy density on a mass basis, as a gas at ambient conditionsit has very low energy density by volume. The techniques employed toprovide hydrogen to portable fuel cell applications are most oftenfocused on chemical compounds that reliably release hydrogen gason-demand. Three broadly accepted mechanisms used to generate hydrogenfrom materials are desorption of metal hydrides, hydrolysis of chemicalhydrides, and thermolysis of chemical hydrides. A combination of thesemechanisms may also be used.

Metal hydrides such as MgH₂, N_(a)AlH₄, and LaNi₅H₆, can be used tostore hydrogen and supply hydrogen on-demand reversibly. However, metalhydride systems often suffer from poor specific energy (i.e., a lowhydrogen storage to metal hydride mass ratio) and poor input/output flowcharacteristics. Hydrogen flow characteristics are driven by theendothemic properties of metal hydrides (the internal temperature dropswhen removing hydrogen and rises when recharging with hydrogen). Becauseof these properties, metal hydrides tend to be heavy and requirecomplicated systems to rapidly charge and/or discharge them. Forexample, commonly owned U.S. Pat. No. 7,271,567 and entitled “FUEL CELLPOWER AND MANAGEMENT SYSTEM, AND TECHNIQUE FOR CONTROLLING AND/OROPERATING SAME,” describes a system designed to store and thencontrollably release pressurized hydrogen gas from a cartridgecontaining a metal hydride or some other hydrogen-based chemical fuel.This system also monitors the level of remaining hydrogen capable ofbeing delivered to the fuel cell by measuring the temperature and/or thepressure of the metal hydride fuel itself and/or by measuring thecurrent output of the fuel cell to estimate the amount of hydrogenconsumed.

Chemical hydrides, such as lithium hydride (L_(i)H), lithium aluminumhydride (LiAlH₄), lithium borohydride (LiBH₄), sodium hydride (NaH),sodium borohydride (NaBH4), and the like, are used to store hydrogen gasnon-reversibly. Chemical hydrides may produce hydrogen upon reactionwith water (hydrolysis) as shown below for two exemplary chemicalhydrides:(Sodium borohydride) NaBH₄+2H₂O→NaBO₂+4H₂(Lithium aluminum hydride) LiAlH₄+4H₂O→4H₂+LiOH+Al(OH)₃

To reliably control the reaction of chemical hydrides with water torelease hydrogen gas from a fuel storage device, a catalyst, andadditives that control the pH of the water feed may be employed. Aninert stabilizer may also be used to inhibit the early release ofhydrogen gas from the hydride. A disadvantage of the hydrolysis route isthe need for providing a water supply, which adds on to the weight andvolume of the fuel cell power system. However, water generated at thecathode may be harvested to supply the water required for the hydrolysisreaction. The harvesting of liquid water without the use of condensersand coolant loops is a challenging problem. In addition, chemicalhydrides compositions that are capable of generating hydrogen usingnear-stoichiometry water requirements may also be required to minimizethe need for an external water supply. On the other hand, the use ofwater vapor offers benefits in the form of better controllability of thehydrolysis reaction and hydrogen release rates. The gradual addition ofwater as water vapor also helps to avoid pressure spikes, and preventsthe occurrence of localized hot spots in the fuel that could lead tothermal decomposition and nm-away reactions.

Traditionally hydrogen producing fuel comprising a chemical hydride andmetal hydride have been used. The fuel may be contained within ahydrogen and water vapor permeable, liquid water impermeable membrane.Upon exposure to water vapor, the chemical hydride produces hydrogen,which may in-part be reversibly adsorbed by the metal hydride. Thedisclosed chemical hydride includes alkali metals, calcium hydride,lithium hydride, lithium aluminum hydride, lithium borohydride, sodiumborohydride and combinations thereof. The fuel cell layer may be wrappedaround the fuel pellet. In addition, a membrane may be disposed within acontainer that is responsive to pressure differences between the insideof the power generator and ambient to regulate the generation ofhydrogen via valves, which may be integral with the fuel cell layer, orotherwise disposed within container. The power generator may include afuel chamber within a generator housing that holds the fuel, which maybe encapsulated or wrapped in a water impermeable, hydrogen and watervapor permeable material. Reaction of the fuel with water vaporgenerated from the fuel cell produces hydrogen gas that is used by thefuel cell to generate electricity. The fuel cell layer is intimatelyintegrated with the fuel to enable capture water vapor produced. Whenthe fuel is consumed, the power generator will need to be disposed forrecycle or refilling. These passive methods and devices are more suitedto support fuel cell power applications that are generally less than 10W (watts). Methods and devices to utilize water vapor generated from afuel cell that is situated external to the fuel supply to enablereplacement of the fuel supply only were not disclosed.

Traditionally a waterless power generator and a passively controlledprocess for producing electricity with a fuel cell using stoichiometricamounts of a solid hydrogen containing fuel and byproduct water vaporproduced by the fuel cell to generate hydrogen gas have been used. Thegenerated hydrogen gas is then consumed in the fuel cell to generateelectrical power and water. The process runs without any attached watersource or water supply other than the water which is produced by thefuel cell. The disclosed generator and operating methods do not permituse of a standalone disposable hydrogen supply (also known as hydrogencartridge) that can generate hydrogen using water vapor produced from afuel cell.

Traditionally a hydrogen generator device that is disposable and nottightly integrated with the PEM fuel cell are known. The hydrogengenerator comprised a chemical hydride fuel pellet core which had aplurality of holes extending through the core. A plurality of polymerictubes formed of water vapor permeable and hydrogen impermeable materialwere disposed in the holes. Cathode air exhaust containing water vaporwas then fed through the tubes. Water vapor selectively permeatedthrough the tubes, reacted with the pellet core, and generated hydrogen,which was routed to the PEM fuel cell. Alternately, wet air exhaust fromthe PEMFC cathode could be fed to the outer wall of the water permeabletubes that contained the fuel. Hydrogen was produced upon reaction withwater vapor and removed from inside the tubes. In either case. the wetair exhaust from the cathode will contain some considerable amounts ofoxygen not consumed in the fuel cell because PEM fuel cells aregenerally run with excess air. Any leakage of oxygen through the waterpermeable membrane tubes raises the potential of creating an explosivemixture with hydrogen produced from the fuel. Further, reactionbyproducts could foul the polymeric tubes and reduce water permeationrates. Finally, when PEM fuel cells a:re nm at constant air flow ratewith variable hydrogen feed rate depending on electrical load, thedriving force for water permeation through the tubes would drop at lowerelectrical loads and would require a more complicated control strategyto perhaps increase the exhaust stream pressure to drive water vaporthrough the tubes.

New and improved methods and devices for generating power using PEM fuelcell power systems that utilize hydrogen generation by hydrolysis ofchemical hydrides, and with minimal water requirement are needed.

DISCLOSURE

Disclosed herein are devices, systems and methods, and aspects thereof,of producing power using a PEM fuel cell power system fed with on demandhydrogen. Aspects of systems and methods include providing fuel pelletsin a rotatable reactor containment insert while controlling the additionof pressurized liquid into said containment insert, then rotating atleast the reactor during liquid feed to generate hydrogen by thehydrolysis of fuel pellets in the reactor: to provide hydrogen via fluidcommunication to the anode side of an open cathode PEM fuel cell stack;and, whereby said fuel cell stack generates electricity.

In some instances the liquid contains between 100% and about 80% waterby volume. In some instances during operation the feeding liquid stepcomprises feeding liquid from a fluid container at a first flow rateduring start-up of the fuel cell stack and reducing the feed rate to arate that is below the first flow rate during normal operation of thefuel cell stack. In some instance at least a portion of the liquid isatomized before it reaches the fuel pellets. The atomizer may be anultrasonic mist generator.

In some instances the fuel comprises lithium aluminum hydride. In someinstance the fuel comprises an admixture of lithium aluminum hydride andan additive comprising at least one of AlCl₃, MgCl₂, BeCl₂, CuCl₂, LiCl,NaCl, and KCl. In some instances the amount of additive in the admixtureis <65 wt.-%.

Disclosed herein are devices systems and methods, and aspects thereof,of producing power using a PEM fuel cell power system fed with on demandhydrogen. Aspects of systems and methods include providing fuel pelletsin a rotatable reactor containment insert while controlling the additionof pressurized liquid into said containment insert, then rotating atleast the reactor during liquid feed to generate hydrogen by thehydrolysis of fuel pellets in the reactor; turbidity fixtures and/orstirring fixtures on the interior surface of the reactor may be addedwhereby turbidity of the fuel pellets is increased during rotation ofthe containment insert as opposed to what occurs with a smooth interior;the system providing hydrogen via fluid communication to the anode sideof an open cathode PEM fuel cell stack; and, whereby said fuel cellstack generates electricity.

In some instances the rotation of the containment insert is accomplishedvia a motor. The fuel pellets may be pressed into predeterminedquantities of fuel. In some instances, via pressing, binders andadditives may be reduced or eliminated. Preferred size range of pelletsis between about 4 mm and about 15 mm in diameter.

Aspects of systems and methods include providing fuel pellets in arotatable reactor containment insert while controlling the addition ofpressurized liquid into said containment insert, then rotating at leastthe reactor during liquid feed to generate hydrogen by the hydrolysis offuel pellets in the reactor: to provide hydrogen via fluid communicationto the anode side of an open cathode PEM fuel cell stack; routinghydrogen to the anode side of the fuel cell stack at a rate that isexcess of that required by the fuel cell stack for producing poweryielding a recirculation hydrogen stream; enriching the recirculationhydrogen exiting the anode with water; and routing the water-enrichedrecirculation stream to the rotatable reactor. In some instances theenriching further comprises: condensing water from the cathode airexhaust; converting the condensed water to a mist comprising a pluralityof water droplets using an atomizer; and entraining the water mist inthe recirculation hydrogen stream. In some instances the enriching stepcomprises splitting the recirculation hydrogen stream into a firstrecirculation stream and a second recirculation stream using a 3-wayvalve and routing the first recirculation stream to a humidifier and thesecond recirculation stream directly to the reactor bypassing ahumidifier.

Disclosed herein are devices systems and methods, and aspects thereof,of producing power using a PEM fuel cell power system, the systemincluding an outer housing; a fuel containment insert configured torotate within the outer housing; a solid fuel inside the reactor of thefuel containment insert; at least one liquid inlet in fluidcommunication with the containment insert; at least one atomizer influid communication with the fluid inlet; at least one hydrogen outletin fluid communication with the containment insert; wherein at least oneof the containment insert and the containment insert and liquid inletare removable from the outer housing. In some instances the fuel pelletsare between about 4 mm and about 15 mm in diameter. A liquid reservoirin fluid communication with the liquid inlet may be added. The liquidreservoir may include an electrical solenoid to open and close liquidflow to the liquid inlet; and, an end cap with an external portion and aplunger portion the plunger portion being driven by a spring configuredto pressurize the fluid reservoir.

In some instances the fluid feed may be via a fluid pump in fluidcommunication with a fluid supply and the fluid inlet.

Disclosed herein are devices, systems and methods, and aspects thereof,of producing power using a PEM fuel cell power system, the systemincluding an outer housing; a fuel containment insert configured torotate within the outer housing; a solid fuel inside the reactor of thefuel containment insert; at least one liquid inlet in fluidcommunication with the containment insert; at least one atomizer influid communication with the fluid inlet; at least one hydrogen outletin fluid communication with the containment insert; at least oneturbidity fixtures and stirring element formed as palt of or affixed tothe interior surface of the reactor; and wherein at least one of thecontainment insert and the containment insert and liquid inlet areremovable from the outer housing.

Disclosed herein are devices, systems, and methods, and aspects thereof,of producing power using a PEM fuel cell power system, the systemincluding an outer housing; a fuel containment insert configured torotate within the outer housing; a solid fuel inside the reactor of thefuel containment insert; at least one liquid inlet in fluidcommunication with the containment insert; at least one atomizer influid communication with the fluid inlet; at least one hydrogen outletin fluid communication with the containment insert; the containmentinsert may further include an outer shell and an inner shell whichtogether further contain a perforated core. Said core is configured tohold solid fuel yet allow reaction byproduct produced during hydrolysisof the fuel to collect outside the core in the inner shell by passingthrough the perforations and the containment insert and liquid inlet areremovable from the outer housing.

In some instances the fuel comprises lithium aluminum hydride. In someinstances the fuel comprises an admixture of lithium aluminum hydrideswith additives that include, but are not limited to AlCl₃, MgCl₂, BeCl₂,CuCl₂, LiCl, NaCl, and KCL. The amount of additive in the admixture isbetween 5 wt.-% and 30 wt.-%.

Disclosed herein are devices, systems, and methods, and aspects thereof,of producing power using a PEM fuel cell power system comprisesproviding a dosed cathode PEM fuel cell stack comprising a plurality offuel cells, each cell having an anode side and a cathode side thatenables operation of the cathode side at substantially ambient pressure.At start-up, water is fed from a water storage to a rotary bed reactorto generate hydrogen by the hydrolysis of a fuel in the reactor.Hydrogen generated from the reactor is muted to the anode side of thefuel cell stack at a rate that is excess of that required by the fuelcell stack for producing power, and a recirculation hydrogen stream. Therecirculation streanl is enriched with water condensed from the cathodeside of the fuel cell stack. The water-enriched recirculation stream isfed to the rotary bed reactor. During nomlal operation, water from thewater storage may not be required or may be used to supplement waterfeed to the reactor. Water is converted to a water mist comprising aplurality of droplets prior to feeding to the rotary bed reactor usingan atomizer, preferably an ultrasonic mist generator. The fuelpreferably comprises of lithium aluminum hydride or mixtures of lithiumaluminum hydride and additives that include, but are not limited to,AlCl₃, MgCl₂, BeCl₂, CuCl₂, LiCl, NaCl, and KCL. Water from the cathodeside may be fed to a secondary water storage, or may be directly routedto the mist generator. Reactant air to the cathode side may beseparately provided to the foe] cell stack, apart from the coolant airto the stack.

Disclosed herein are devices, systems, and methods, and aspects thereofof producing power using a PEM fuel cell power system comprisesproviding an open cathode PEM fuel cell stack comprising a plurality offuel cells. The flow at the cathode side exit is restricted to drivewater from the cathode side to the anode side. Water is fed from a waterstorage to a rotary bed reactor to generate hydrogen by the hydrolysisof a fuel in the reactor at start-up. Hydrogen is routed to the anodeside of the fuel cell stack at a hydrogen flow rate sufficient forproducing power, and a water enriched recirculation hydrogen stream. Therecirculation stream may be additionally enriched in water content usingwater from a water storage. Water from the water storage is preferablyconverted to mist prior to feeding to the reactor.

Disclosed herein are devices, systems, and methods, and aspects thereof,of producing power using a PEM fuel cell power system comprisesproviding an open cathode PEM fuel cell stack comprising a plurality offuel cells feeding water from a water storage to a rotary bed reactor togenerate hydrogen by the hydrolysis of a fuel in the reactor; androuting hydrogen to the anode side of the fuel cell stack at a hydrogenflow rate sufficient for producing power. Hydrogen recirculation orwater recovery steps are not used. Water is converted to a water mistcomprising a plurality of droplets prior to feeding to the rotary bedreactor using an atomizer, preferably an ultrasonic mist generator.

Disclosed herein are devices, systems, and methods, and aspects thereofof a rotary bed reactor for use in the fuel cell power system comprisesan outer stationary housing having a water inlet in fluid communicationwith a water storage, a cylindrical insert that is rotatable disposedwithin the outer housing and having a plurality of feed openings influid communication with the water inlet of the stationary housing andan outlet for removing hydrogen. A fuel, preferably lithium aluminumhydride, calcium hydride, sodium aluminum hydride, sodium hydride,aluminum hydride in the form of particles is provided inside the insert.Hydrogen is generated by the hydrolysis of the fuel with water andremoved from the outlet. Water is preferably fed in the form of a watermist to the reactor. The mist may be generated using an atomizer thatmay be closely coupled to the water inlet. The fuel may also comprise ofmixtures of lithium aluminum hydride, calcium hydride, sodium aluminumhydride, sodium hydride, aluminum hydride and additives that include,but are not limited to, AlCl₃, MgCl₂, BeCl₂, CuCl₂, LiCl, NaCl, and KCl.

Other features and advantages of the present disclosure will be setforth, in part in the descriptions which follow and the accompanyingdrawings, wherein the preferred aspects of the present disclosure aredescribed and shown, and in part, will become apparent to those skilledin the art upon examination of the following detailed description takenin conjunction with the accompanying drawings or may be learned bypractice of the present disclosure. The advantages of the presentdisclosure may be realized and attained by means of theinstrumentalities and combinations particularly pointed out in theappendant claims.

DRAWINGS

The foregoing aspects and many of the attendant advantages of thisdisclosure will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a schematic diagram of an exemplary implementation of anopen cathode fuel cell power system with hydrogen recirculation thatcaptures a substantial amount of water required for hydrogen generation.

FIG. 2 shows a schematic diagram of an exemplary embodiment of theaspect shown in FIG. 1 that does not use a humidifier.

FIG. 3 shows a schematic diagram of an exemplary aspect of a dosedcathode fuel cell power system with hydrogen recirculation that capturesa substantial amount of water required for hydrogen generation.

FIG. 4 shows a schematic diagram of another exemplary aspect of a fuelcell power system with hydrogen recirculation that captures asubstantial amount of water required for hydrogen generation from theanode side of the fuel cell.

FIG. 5 shows a schematic diagram of an exemplary implementation of anopen cathode fuel cell power system without hydrogen recirculation orwater recovery.

FIG. 6 shows hydrogen yield as a function of time during hydrolysis oflithium aluminum hydride in a fixed bed reactor.

FIG. 7 shows hydrogen flow rate as a function of hydrogen yield duringhydrolysis of lithium aluminum hydride in a fixed bed reactor.

FIGS. 8(a) to FIGS. 8(c) shows various views of an exemplary rotary bedreactor for use in fuel cell power systems: FIG. 8(a) is cross sectionview; FIG. 8(b) is an exploded view (outer tube not shown); and FIG.8(c) is a perspective view with the outer tube cut open.

FIG. 9 shows hydrogen yield as a function of time during hydrolysis oflithium aluminum hydride in a both rotary bed and fixed bed reactors.

FIG. 10 shows hydrogen flow rate as a function of hydrogen yield duringhydrolysis of lithium aluminum hydride in a both rotary bed and fixedbed reactors.

FIG. 11 shows various views of an exemplary 3-way valve for controllingthe flow of hydrogen recirculating stream (FIG. 1 ) to the humidifier.

FIG. 12(a) shows a sectional perspective view of an exemplary rotary bedreactor; FIG. 12(b) shows the drive assembly that mates with therotating parts of the reactor.

FIG. 13 shows a cut away view of an assembled rotary reactor withpressurized fluid feed.

FIG. 14 shows an assembly view of a rotary reactor.

FIG. 15 shows a cut-away view of a rotary reactor and fluid pumpconfigured to attach to a fluid supply.

The components in the figures are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the disclosure.All reference numerals, designators and callouts in the figures andAppendices are hereby incorporated by this reference as if folly setforth herein. The failure to number an element in a figure is notintended to waive any rights. Unnumbered references may also beidentified by alpha characters in the figures. All callouts in figuresare hereby incorporated by this reference as if fully set forth herein.

The following detailed description includes references to theaccompanying drawings, which form a part of the detailed description.The drawings show, by way of illustration, specific embodiments in whichthe fuel cell systems and methods may be practiced. These embodiments,which are also referred to herein as “examples” or “options,” aredescribed in enough detail to enable those skilled in the art topractice the present invention. The embodiments may be combined, otherembodiments may be utilized or structural or logical changes may be madewithout departing from the scope of the invention. The followingdetailed description is, therefore, not to be taken in a limiting senseand the scope of the invention is defined by the appended claims andtheir legal equivalents.

In this document, the terms “a” or “an” are used to include one or morethan one, and the term “or” is used to refer to a nonexclusive “or”unless otherwise indicated. In addition, it is to be understood that thephraseology or terminology employed herein, and not otherwise defined,is for the purpose of description only and not of limitation.

DETAILED DISCLOSURE

Particular aspects of the disclosure are described below in considerabledetail for the purpose for illustrating its principles and operation.However, various modifications may be made, and the scope of theinvention is not limited to the exemplary aspects described.

The fuel cell power system schemes described below target methods anddevices that lead to efficient and lightweight power systems forapplications such as unmanned aerial vehicles. In one aspect 100 (FIG. 1), air is fed to the cathode side of an open cathode PEM fuel cell stack103 through manifold 102 using a low pressure blower 101. PEM stack 103is generally an air cooled stack, although in some instances it may becooled by a coolant. The cathode side of the open cathode fuel cellstack operates substantially at ambient pressure, and generally lessthan 10 psi. As described above, water is generated at the cathode sideof fuel cell stack 103 which humidifies the air as it leaves fuel cell111 through outlet manifold 104. Humidified air (relative humidity couldbe as high as 90%) is routed to humidifier 105, exchanges water with therecirculation hydrogen stream from the anode side exhaust, and is ventedout. At start-up, water stored in water storage 106 is fed to reactor109. Preferably, water is fed to an atomizer 108, preferably anultrasonic mist generator, using pump 107, where water is converted to afog or mist comprising tiny water droplets 1 micron to 100 micron indiameter, and preferably 10 micron and 15 micron in diameter. The watermist is then fed to reactor (or cartridge) 109 and reacts with fuelcontained therein to produce hydrogen by hydrolysis. The fuel maycomprise lithium aluminum hydride (LAH) or other chemical hydrides thatproduce hydrogen by hydrolysis. The dry hydrogen stream is then fed tothe anode side of fuel cell stack 103 in excess of the flow raterequired to produce the target power from fuel cell 111. Unreactedhydrogen (recirculation hydrogen stream) is routed to humidifier 105using a recirculation blower 110, where it exchanges water from thehumidified air that exits the fuel cell 111. This water enrichedrecirculation hydrogen stream, then entrains the mist from atomizer 108and enters reactor 109. During steady state operation, it is expectedthat the water enriched hydrogen recirculation stream will supply thewater required for hydrolysis in reactor 109; that is make-up water fromwater storage 106 may not be required during normal operation. Thestart-up reservoir 106 may be built in to reactor 109 with a suitablewater delivery mechanism. Reservoir 106 could be made of flexiblepolymeric materials. In some instances, for example, to supportincreased hydrogen generation rates required by peak loads, water fromwater storage 106 may continue to be fed to atomizer 108 during normaloperation at a flow rate that is usually below the flow rate used duringstart-up. While a preferred water atomizer is the ultrasonic mistgenerator, other options such as a modified fuel injector used incombustion engines may be used. For example, micro spray nozzles thatgenerate a fine spray (e.g. The Lee Company nozzles) may be used.

The fuel cell power system may optionally include a hydrogen storagecomponent (e.g. metal hydride) that may provide hydrogen required forstart-up. In this case, water for start-up may not be required. Thehydrogen storage component may be recharged with the hydrogen that isproduced. The fuel cell power system may also contain a small Li-ionbattery for providing power during start-up and for handling peak loads.

In the fuel cell system described in FIG. 1 , the hydrogen generationrate may be controlled by bypassing the humidifier, in full or in-part,when needed. A 3-way valve may be used for this purpose. A hydrogengeneration rate in reactor 109 that exceeds the hydrogen consumptionrate in the fuel cell system would likely increase the pressure inreactor 109. A suitable feedback signal may be sent to the 3-way valve,which may respond by routing the recirculation stream away fromhumidifier 105; that is, in some instances, the recirculating streamwould bypass humidifier 105 and be routed directly to reactor 109. Thisreduces the amount of water fed to the fuel in reactor 109, which inturn would reduce hydrogen production. The 3-way valve may also bedesigned to split the recirculation hydrogen stream into two streams.The first fraction of the recirculation stream bypasses the humidifierwhile the second fraction of the recirculation stream flows into thehumidifier. This flow splitting may be used to fine-tune the amount ofwater that enters reactor 109 and could achieve hydrogen control within+/−5 sccm or +/−20 mbar. FIG. 11 shows an exemplary 3-way valve 1100.Valve 1100 comprises a single inlet port 1101 that is in fluidcommunication with outlet ports 1102 and 1103 through an intermediatefluid chamber 1104. Fluid chamber 1104 comprises valve openings 1105 and1106 that communicate with the outlets 1102 and 1103 respectively. Valveopenings 1105 and 1106 may be closed by sealing disks 1107 and 1108respectively. The sealing disks are mounted on valve piston 1109 andheld in place by a plurality of supporting members 1110. The linearreciprocal motion of piston 1109 urge one of the sealing disks to closea valve opening, while the other disk remains open. The shaft motion maybe enabled by a suitable motor ˜md crankshaft components or rocking beamor other mechanisms, generally shown as 1111. Bellow type seals 1112 maybe used to seal the piston 1109 to the valve body. Instead of using flatsealing disks that are amenable to switching flow between outlets 1102and 1103, conical typical sealing disks or other suitable sealingcomponents may be used to partially open openings 1105 and 1106 androute the inlet flow to both outlets 1102 and 1103, thereby facilitatingthe control of the ex-tent of flow to each outlet in a predeterminedmanner.

FIG. 2 shows one embodiment of the first aspect of the fuel cell powersystem, wherein humidifier 105 is not used. Instead, cathode exhaust iscompressed using compressor 112 such that water condenses out withoutany coolant loops into condenser 113. The exiting air from condenser 113may be exhausted through an ejector 115 to supplement cooling air ifnecessary to the fuel cell 111. Alternately, the exiting air fromcondenser 113 may be vented out. Condensed water from condenser 113 maybe routed to water storage 106 using a pump 114. Alternately, condensedwater may be fed to atomizer 108 and entrained into reactor 109 by therecirculation hydrogen stream. In some instances, coolant air to thestack is separately provided using a blower, while an air ptmlp mayprovide reactant air to the cathode side of stack 103.

In a second aspect of the fuel cell power system, water recovery fromthe fuel cell may be accomplished without the use of a condenser or ahumidifier. In the scheme 200 (FIG. 3 ), PEM fuel cell 211 comprises adosed cathode stack. The dosed cathode stack operates the cathode sideat a pressure above ambient pressure. Closed cathode stack 203 mayrequire the stack coolant air flow to be separate from the reactant airfeed to the cathode side of each cell in the stack. Coolant air fromblower 201 may be used to pressurize an array of piezoelectric air pumpsthat are mounted to the inlet air manifold (not shown). Alternately,reactant air may be fed using a diaphragm pump or a centrifugal blower.Since the cathode is closed, the cathode side is pressurized, whichencourages the formulation of water condensate at the outlet of thecathode or in the cathode manifold 204. The manifold 204 may comprise ofcondenser components (heat exchanger). Condensed water may beperiodically removed using pump 214 and routed to water storage 206. Inaddition cathode exhaust gas (unreacted oxygen, nitrogen, uncondensedwater) may be vented from cathode exhaust manifold 204. At start-up,water stored in water storage 206 is fed to atomizer 208, preferably anultrasonic mist generator, using pump 207, where the water feed isconverted to a fog or mist comprising tiny water droplets 1 micron to100 micron in diameter, and preferably 10 micron and 15 micron indiameter. The water mist is then fed to reactor (or cartridge) 209 whereit reacts with fuel to produce hydrogen by hydrolysis. The fuel maycomprise of lithium aluminum hydride (LAH) or other chemical hydridesthat produce hydrogen by hydrolysis. The dry hydrogen stream is then fedto the anode side of fuel cell 211 in excess of the flow rate requiredto produce the target power from fuel cell 211. Alternately, hydrogenexiting reactor 209 may be split into a hydrogen feed stream and ahydrogen recirculation stream. The hydrogen feed stream is fed to theanode side of fuel cell 211 using hydrogen pump or blower 215, and therecirculation stream is routed to reactor 209. When water is fed toatomizer 208, the recirculation hydrogen stream may be used to entrainthe water mist into reactor 209. Hydrogen exiting the reactor 209 may besplit into a hydrogen feed stream and a hydrogen recirculating stream bythrottling the hydrogen recirculating stream using restrictor 216instead of, or in addition to using pump 215. Any unreacted hydrogenexiting the anode is also recirculated to atomizer 208. During normaloperation, it is expected that the condensed water from the cathode sideof stack 211 will supply the water required for hydrolysis in reactor209; that is make-up water from water storage 206 will not be required.The start-up water 206 reservoir may be built in to reactor 209 with asuitable delivery mechanism. Condensed water may also be fed to theinlet of pump 207. Alternately, condensed water may be collected inwater storage that is separate of storage 206. Atomizer 208 may beclosely coupled to reactor 209 to avoid condensation of the waterdroplets in the mist.

A single air blower may be used to provide both reactant air and coolantair to fuel cell 211. In this case, active cooling of the watercollection components 204 may be required using water from the waterstorage 206. Uncondensed gases (unreacted oxygen, nitrogen) in thecathode exhaust would have to be vented at a suitable point: forexample, from the water storage 206 or a gas/liquid separator such as aflash tank. Use of a closed cathode stack in fuel cell 211 may require astack purge after change out of reactor 209 using an inert gas.

In a third aspect of the fuel cell power system (FIG. 4 ), the cathodeside of stack 303 in fuel cell 311 is restricted to urge water todiffuse to the anode side from the cathode side. Therefore, there is nowater recovery from the cathode side. As shown in FIG. 4 , air is fed tostack 303 using an air blower 301. At start-up, water from storage 306is fed to ultrasonic atomizer 308 using pump 307, where the water feedis converted to a fog or mist comprising tiny water droplets 1 micron to100 micron in diameter, and preferably 10 micron and 15 micron indiameter. The water mist is then fed to reactor (or cartridge) 309 whereit reacts with fuel to produce hydrogen by hydrolysis. The fuel maycomprise of lithium aluminum hydride (LAH) or other chemical hydridesthat produce hydrogen by hydrolysis. The relatively dry hydrogen gasexiting reactor 309, with relative humidity between 1% and 40%, andpreferably between 5% to 15%, at ambient temperature, may be split intoa hydrogen feed stream and a hydrogen recirculation stream. Hydrogenexiting the reactor 309 may be split into a hydrogen feed stream and ahydrogen recirculating stream by throttling the hydrogen recirculatingstream using restrictor 316; alternately, hydrogen stream splitting maybe enabled by using a hydrogen feed pump (as shown in FIG. 3 ) in lieuof, or in addition to flow restrictor 316. Hydrogen feed to the anodeside of fuel cell 311 is preferably in excess of the flow rate requiredto produce the target power from fuel cell 311 to ensure that somehydrogen exits the anode side. The recirculation hydrogen stream isfurther enriched in water content when it is routed to atomizer 308 toentrain the water mist into reactor 309. Any unreacted hydrogen exitingthe anode is also routed to atomizer 308. During steady state operation,it is expected that the condensed water from the anode side (water istransported to the anode of stack 303 due to the restricted cathode flowdesign of stack 303) of stack 303 will be carried by the recirculatinghydrogen stream to supply the water required for hydrolysis in reactor309. The start-up 306 reservoir may be built in to reactor 309 with asuitable delivery mechanism. Atomizer 308 may be closely coupled toreactor 309 to avoid condensation of the water droplets in the mist.

The requirements of the target fuel cell power application generallydictates the choice between open cathode fuel cell stack schemes (FIGS.1 to FIGS. 2 ) involving hydrogen recirculation, and closed cathode fuelcell stack schemes (FIGS. 3 to FIGS. 4 ). An open cathode stack may berelatively lighter in weight than a closed cathode stack, but generallyrequires the use of other components such as condensers and humidifiersto capture water, and the additional mass of these components in somecircumstances may offset potential weight reduction benefits afforded bythe lightweight stacks. On the other hand, dose cathode stack schemesmay not generally require external components such as humidifiers andcondensers, but are characterized by relatively higher stack mass, andmay require a purge step after reactor (cartridge) changeover.Applications that specify near-zero external water requirements (e.g.military applications) may require a close examination of trade-offsbetween weight reduction and system complexity.

When applications permit the use of external water, but require a simpleand lightweight fuel cell power system, schemes that do not involvehydrogen recirculation may be considered. FIG. 5 illustrates such a fuelcell power system (500), water required for the hydrolysis is containedin fluid storage 506 and is fed to an atomizing fixture 508 such as anatomizer or nozzle using pump 507 or fluid under pressure via spring orother compression producing force. The mist exiting the atomizer 508 isrouted to reactor 509 where hydrogen is generated and is fed to theanode side of open cathode fuel cell stack 503 of fuel cell 511. Bothcooling and reactant air may be fed to the cathode using blower 501.Atomizer 508 may be removably coupled to reactor 509 to prevent anycondensation of droplets from the mist. Condensation may also beminimized or eliminated by the use of electrical heating if needed. Asshown in FIG. 5 , process scheme 500 does not require liquid recoveryfrom stack 503 or hydrogen recirculation.

In the above aspects and their embodiments, components that include, butare not limited to, liquid feed pump or spring or other mechanism forproducing pressurized water, atomizer or atomizing nozzle, micro watercontrol valve, reactor, hydrogen pumps, water storage, and the hydrogenrecirculation stream flow restrictor may be interchangeably used. Theliquid feed pump could comprise of a miniature piezoelectric pump orother micro pump designs that can output 300 ml/h of water to generatehydrogen from LAH to support a 400 We, 750 We-h fuel cell power system.The parasitic power requirement of the pump is expected to be below 0.5W. Alternatively, the parasitic loss due to the water pump can besubstantially reduced by replacing the water pump with a springmechanism that pressurizes the water reservoir and, when coupled with amicro water valve, allows water to be controllably dispensed through theatomizing nozzle. The atomizer may be closely coupled to reactor toprevent condensation of water into large droplets. The parasitic powerrequirement for an ultrasonic atomizer is expected to be less than 5 W.Water storage may be in the form of a flexible bladder that can store 50g to 300 g of water depending on the requirements of a particularapplication. The hydrogen recirculation blower is also lightweight (<150g) with a preferable capacity of at least 50 SLPM at 50 mbar.

Any feasible combination of the concepts described above may be employedto yield a suitable fuel cell power system. For example, in processschemes that use either open cathode or closed cathode stacks withoutthe use of hydrogen recirculation, dry hydrogen exiting the reactor maybe humidified by cathode air exhaust (using a suitable humidifier) priorto feeding to the anode side of the stack. Using humidified hydrogen isknown to increase the lifetime of air cooled PEM fuel cell stacks.

The process schemes and fuel cell power systems described above systemrequire hydrogen generation at a sufficient rate in the reactor tosupport the power output from the fuel cell as well as maintain therecirculation rate required. The inventors observed unsatisfactoryhydrogen generation rates and yields during vapor phase hydrolysis in aconventional fixed bed reactor. As shown in FIG. 6 , the hydrogen yieldflattens out at about 85% at about 3.8 h during vapor phase hydrolysisof LAH in a fixed bed reactor. Hydrogen yield is defined as the amountof hydrogen produced as a fraction the theoretical amount of hydrogencontained in the chemical hydride fuel. The fixed bed comprised of fuelin the form of pellets 4 mm to 15 mm in size. Fluid such as water orwater containing fluid is fed in the form of mist using an ultrasonichumidifier. Nozzles that provide a fine mist spray may also be used.Further as shown in FIG. 7 , a constant hydrogen flow rate of 0.11 SLPMwas measured at yields <25%), after which a reduction in the flow ratewas observed. Without intending to be bound by any particular theory, itis believed that the hydrogen generation degrades as the fuel isutilized partially due to the accumulation of reaction byproducts in thereactor, and in particular on the unreacted fuel particles. When thisoccurs the reactivity of the unreacted fuel particles is significantlyreduced, and hydrogen production rate is subsequently significantlyreduced. Reaction products that form early on in the life of a fuelcharge to the reactor (hydrogen cartridge) essentially block theunderlying fresh fuel material. Recirculating humidified hydrogen mayfurther humidify the byproducts such as lithium hydroxide (LiOH),lithium chloride (LiCl), and lithium aluminum hydroxide, LiAl₂(OH)₇,which further reduces the amount of water that is available to reactwith fresh fuel. To offset this reduction in hydrogen generation ratethroughout the life of the fuel in the hydrogen generator, excess fuelis generally required, which adds on the mass of the hydrogen generator.Excess fuel mass also increases the cost of the hydrogen generator.Conventional fixed bed reactor designs are therefore not suitable forvapor phase hydrolysis. Other novel reactor designs are required tomaintain sufficiently steady hydrogen generation rates throughout thelife of the fuel.

A reactor that is suitable for use in the above described processschemes is a rotary bed reactor or rotatable reactor. An exemplaryrotary bed reactor 800, as shown in FIGS. 8(a) to FIGS. 8(c), comprisesa cylindrical reactor insert 801 that is configured to be rotated in anouter tube 802. End 803 of insert 801 is configured to couple to one endof rotor shaft 804, and is rotated by connecting to a gear train 805 andbrushless motor 806. Water is fed to water inlet 808, which is in fluidcommunication with a plurality of water inlet holes 808 in end 803.Water is preferably fed as a mist or vapor, although liquid water mayalso be used. Hydrogen generated is removed through outlet 809 disposedin outlet lid 812, and through a corresponding outlet 813 m tube 802(not shown). Outlet line 812 can be removed connected to insert 801, forexample, can be screwed into insert 801. The walls of insert 801comprise a plurality of slits 810 to allow for preferential removal ofreaction byproducts from inside the insert that is urged by the rotarymovement of insert 801. Fuel (e.g. LAH or CaH) in the form of pellets ortablets is loosely packed inside insert 801, which reacts with water togenerate hydrogen. The rotary movement of the insert keeps the fuelparticles in continuous motion and prevents the accumulation ofbyproducts on the unreacted fuel. Since outer tube 802 is stationary,rotary bed reactor 800 may be operated in any orientation, althoughoperation in the horizontal orientation is preferred. Insert 801 alsohas a plurality of plastic piston ring seals 811 that seal the insert801 to the inner wall of outer tube 802, and prevents water mist feedfrom bypassing the fuel particles inside insert 801. Ports 808 andoutlet 813 can be interchangeably used; for example, port 808 may beused as the outlet for hydrogen and 813 as the inlet for the water feed(mist). Suitable filters may be used downstream of outlets, fix exampledownstream of 809 when port 808 is used as the inlet, to preventparticles from clogging the hydrogen outlet. Temperature sensor 814 maybe used to monitor the temperature of reactor 800. For an approximately400 W_(e), 750 W_(e)-h fuel cell system, insert 801 is preferably 3 inchto 5 inch in length and 3 inch to 5 inch in diameter. The amount of LAHfuel required would be about 300 g.

Table 1 shows the forecasted specific energy and specific power using anopen cathode fuel cell power system nm without hydrogen recirculation orwater recovery. A rotary bed reactor is used. The specific energy ofabout 550 We-h/kg is >2× better than Li-ion batteries. The specificpower of about 290 W-e/kg is >5× better than that disclosed in U.S. Pat.No. 9,005,572 for a 33 We fuel cell power system.

TABLE 1 Metric Value Energy (W-h) 750 Power (W) 400 Fuel Cell stack (g)250 Power/control electronics (g) 60 Li-ion battery (g) 120 Fluidiccircuitry (g) 10 LAH Fuel Cartridge (g) 450 Case (g) 80 Total (g) 1370Specific Energy (Wh/kg) 547 Specific Power (W/kg) 292

FIG. 9 shows the drastic improvement in hydrogen yields compared to thatmeasured using the fixed bed reactor. As can be seen, 99% yield wasachieved in <1 h of run time. Further, as shown in FIG. 10 , >2×increase in hydrogen flow rates were measured at hydrogen yields of upto 50%. These results demonstrate that hydrolysis of LAH in the rotarybed reactor results in faster hydrogen generation rates and improvedfuel utilization than the fixed bed reactor. Therefore, the amount offuel required to support power production in a fuel cell system isreduced, which in turn would increase the specific energy (W-h/kg) andenergy density (W/kg) of the fuel cell system.

FIG. 12(a) illustrates another exemplary rotary bed reactor 1200. Thereactor comprises concentric shells 1201 and 1202. Outer shell 1201 maybe made of aluminum and is stationary. Inner shell 1202 may be made ofinjected molded plastic that includes PEEK and ULTEM and is configuredto be tumbled or rotated. Shell 1202 is configured to receive aperforated cylindrical core 1203 that has a plurality of slits orperforations 1204 on its ‘wall.

Perforated core is configured to engage with driven gear 1205 and maypreferably rotate (along with shell 1202) at 2 rpm to 25 rpm. Perforatedcore 1203 may be made of injected molded plastic that includes PEEK andULTEM and has first end 1207 and a second end 1208 opposite to the firstend. End 1208 may be closed using a plastic end cap 1209. Fuel (e.g.LAH) particles are disposed in the region 1206 between shell 1202 andperforated core 1203. Assembly 1210 shown in FIG. 12(h) has a sealingsurface 1215 that is configured to from a lip seal with a mating surfacein reactor 1200 as shown in FIG. 12(a). Assembly 1210 comprises a waterinlet port 1212, a hydrogen exit port 1211 and a shaft 1213 thatmechanically connects drive gear 1216 to a suitable motor. Filtermaterials may be housed inside assembly 1210 upstream of hydrogen port1211 to filter and remove any dust, or other contaminants from hydrogengas. The water inlet port 1212 is in fluid communication with a spraynozzle (or a plurality of nozzles) 1214. Drive gear 1216 engages withdriven gear 1205 and when the motor is energized, tumbles core 1203 andinner shell 1202. The water atomizing nozzle sprays water through theperforations 1204 to contact the fuel particles in region 1206. The slowtumbling movement of shell 1203 helps to expose the fuel particles towater droplets or mist in a substantially uniform manner. In addition,build-up of reaction byproducts on the unreacted fuel particles isminimized or substantially eliminated.

As described above, water mists may be generated using an atomizer. Ithas been found that using water in the form of a mist (dispersed waterdroplets) increases the hydrogen generation rate compared to watervapor. When water is in the form of a mist, the water droplets increasesthe actual mass of water per unit volume entering the reactor. Comparedto humidified recirculating hydrogen that contains water vapor, the useof water mist increases the rate of hydrogen generation and fuelutilization. Devices such as fuel injector for combustion engines mayalso be modified and used to atomize water and generate the water sprayor mist. Strictly controlling the mist output rates would avoid issuessuch as start/stop outgassing or pressure spikes commonly seen whenfeeding liquid water.

FIGS. 13 and 14 illustrate another exemplary rotary reactor forgenerating hydrogen when applications pem lit the use of supplied orexternal water. The system includes a containment insert 1000 comprisingat least a rotatable fuel reactor 509 with an interior surface 510having distal end 530 adjacent to a hydrogen output connection 650 and aproximal end 520 adjacent the reactor fluid input 508′, an outputconnection 650 and an mating guide 612 which forms a fluid interface 610between the containment insert 1000 and a fluid container 506 via thecooperating mating guide 614 on the fluid container. The rotatable fuelreactor 509 may be generally an annular walled or cylindrical form witha homogeneous or non-homogenous interior surface 510. The interiorsurface may have turbidity fixtures 602 formed thereon. Such turbidityfixtures may be in the form of raised or lowered texture regions,protrusions, depressions, bumps or divots in a regular or irregularpattern which vary the interior surface and promote turbidity of thepellets during rotation. An extended partial wall or other stirringelement 604 may be added to at least one of the proximal and distal ends520/530. The reactor may be formed of light weight thin walled metals orpolymers or insulators which contain fuel which may be in the form ofpressed pellets 600 between about 4 mm to 15 mm in size. Thin walledmaterials, in some instances have less thermal mass then thickermaterial and will cool faster. Insulators limit some heat transfer.

The fluid container 506 with an interior surface 506′ is also provided.The rotatable fuel reactor 509 and fluid container 506 connect via themating guide 612 and the cooperating mating guide 614 at a fluidinterface 610. The connection provides for controlled fluid delivery tothe containment insert 1000 and disassociation of at least one of thefluid container and the containment insert 1000 from the system. Thedisassociation includes removal and replacement. The fluid container 506may be reversibly sealed via a cap 513. The fluid container mayberefillable. Fluid is kept at pressure above ambient pressure preferablybetween 5-50 psi to maintain adequate fluid pressure for atomization ofthe fluid through the atomizing nozzle 508. Fluid can be kept atpressure by various mechanisms including external pump or viaintegration of a spring 512 and cap 513. The spring 512 provides a forceby which the interior portion of the end cap acts as a plunger to exertpressure on the fluid in the fluid container. Fuel reactor 509 isrotated by motor 514. Fluid injection rate through the atomizer 508 maybe controlled via a solenoid valve 515 that is actuated and may becontrolled via a microprocessor or controller. A fluid input 625provides a fluid connection via the solenoid valve to the atomizer 508.Fluid in the form of mist exit at the reactor fluid input 508′ when thefluid entering the atomizer is pressurized. Those of ordinary skill inthe art will recognize that a plentitude of controllers exist in the artand the invention scope is not limited to one particular control scheme.The control may be deployed based on at least one of fluid pressure,hydrogen pressure, hydrogen flow, temperature. time, hydrogen output,voltage or other measured system parameter(s). Optionally, a removablelightweight protective outer shell 516 may be added. To reduce cost, allcomponents can be reusable and/or refillable. The rotating mechanismsuch as a motor or motor and gear system 514 is configured to rotate thereactor while leaving the hydrogen output connection 650 free to connecta fuel cell 700 or other hydrogen using or storing device. Between theoutput connection 650 and the inside of the reactor 509′ is a filter 690to prevent fine particles from being passed into the H2 output stream. Acontrol valve 675 may be added to at least one of relive pressure in anover pressurized system or to prevent backflow when hydrogen productionis halted. Fluid may be between 100% and about 80% water by volume. Insome instances heat exchange fixtures such as fins 900 are added to, orformed as part of, the fuel reactor 509. In some instance the heatexchange fixtures 900 may form a part of the turbidity fixtures. In someinstances extended fins 900 from the exterior of the reactor coincidewith raised or lowered regions on the interior of the reactor.

Turbidity fixtures may be sized and/or positioned to enhance dispersionof fuel pellets during hydrolysis. By sizing and spacing the turbidityfixtures to correspond to the fuel pellet size and shape greaterexposure of fluid to fuel is achieved and spent fuel which may crustonto the pellet is dislodged thereby exposing fuel. A system whichmatches fuel pellet morphology and turbidity fixtures may improve energydensity.

FIG. 15 illustrates an assembly 750 utilizing a fluid pump 750 in fluidconnection with the containment insert 1000 to deliver pressurized fluidto the atomizer 508. The solenoid illustrated in FIG. 13 is replacedwith the pump 800. The pump has an input 802 and output 804 whereby theoutput is configured to supply fluid to the atomizer 508. The rotatingreactor is configured to rotate at the fluid interface 610.

Suitable fuels for use in the rotary bed reactor as described in thisdisclosure include lithium aluminum hydride (LAH), with purity of atleast 95%. The fuel is preferably formulated in the form of particles ortablets. If needed, certain additive materials such as activation agentsor catalysts may be added to LAH to maximize hydrogen production fromthe fuel. Exemplary fuels and materials include, but are not limited to,those disclosed in commonly owned U.S. Pat. No. 8,636,961, and entitled“FUELS FOR HYDROGEN GENERATING CARTRIDGES.” which is incorporated byreference herein in its entirety. Exemplary fuels and materials may alsoinclude, but are not limited to those disclosed in, U.S. Pat. No.7,393,369, entitled “APPARATUS, SYSTEM, AND METHOD FOR GENERATINGHYDROGEN,” U.S. Pat. No. 7,438,732, entitled “HYDROGEN GENERATORCARTRIDGE,” and U.S. Pat. No. 8,357,213, entitled “APPARATUS, SYSTEM,AND METHOD FOR PROMOTING A SUBSTANTIALLY COMPLETE REACTION OF ANANHYDROUS HYDRIDE REACTANT,” which are all incorporated by referenceherein in their entirety. Preferable additives include chloride saltsthat include, but are not limited to, AlCl₃, MgCl₂, BeCl₂, CuCl₂, LiCl,NaCl, and KCl. The amount of these additives in the fuel could be up to65 wt.-%. Preferably, the amount of these additives in the fuel isbetween about 5 wt.-% and about 30 wt-%. A preferred alternative is touse LAH without any additives and to use preferred reactor designs suchas the rotary bed reactor as described above. Other fuel candidatesinclude sodium aluminum hydride, sodium borohydride, and sodiumsilicide.

Air cooled stacks and methods of operation of the stacks are describedin commonly owned U.S. Pat. No. 8,263,277 entitled “REHYDRATION OF FUELCELLS,” and U.S. Pat. No. 8,323,846 entitled “FUEL CELL GASDISTRIBUTION,” which are incorporated by reference herein in theirentirety.

The Abstract is provided to comply with 37 C.F.R. § 1.72(b), to allowthe reader to determine quickly from a cursory inspection the nature andgist of the technical disclosure. It should not be used to interpret orlimit the scope or meaning of the claims.

Although the present disclosure has been described in connection withthe preferred form of practicing it, those of ordinary skill in the artwill understand that many modifications can be made thereto withoutdeparting from the spirit of the present disclosure. Accordingly, it isnot intended that the scope of the disclosure in any way be limited bythe above description.

While the methods and fuel cell power systems have been described interms of what are presently considered to be the most practical andpreferred implementations, it is to be understood that the disclosureneed not be limited to the disclosed implementations. It is intended tocover various modifications and similar arrangements included within thespirit and scope of the claims, the scope of which should be accordedthe broadest interpretation so as to encompass all such modificationsand similar structures. The present disclosure includes any and allimplementations of the following claims.

It should also be understood that a variety of changes may be madewithout departing from the essence of the disclosure. Such changes arealso implicitly included in the description. They still fall within thescope of this disclosure. It should be understood that this disclosureis intended to yield a patent covering numerous aspects of thedisclosure both independently and as an overall system and in bothmethod and apparatus modes.

Further, each of the various elements of the disclosure and claims mayalso be achieved in a variety of manners. This disclosure should beunderstood to encompass each such variation, be it a variation of animplementation of any apparatus implementation. a method or processimplementation, or even merely a variation of any element of these.

Particularly, it should be understood that as the disclosure relates toelements of the disclosure, the words for each element may be expressedby equivalent apparatus terms or method terms—even if only the functionor result is the same.

Such equivalent, broader, or even more generic terms should beconsidered to be encompassed in the description of each element oraction. Such terms can be substituted where desired to make explicit theimplicitly broad coverage to which this disclosure is entitled.

It should be understood that all actions may be expressed as a means fortaking that action or as an element which causes that action.

Similarly, each physical element disclosed should be understood toencompass a disclosure of the action which that physical elementfacilitates.

Any patents, publications, or other references mentioned in thisapplication for patent are hereby incorporated by reference. Inaddition, as to each term used it should be understood that unless itsutilization in this application is inconsistent with such interpretationcommon dictionary definitions should be understood as incorporated foreach term and all definitions, alternative terms, and synonyms such ascontained in at least one of a standard technical dictionary recognizedby artisans and the Random House Webster's Unabridged Dictionary, latesteditions are hereby incorporated by reference.

To the extent that insubstantial substitutes are made, to the extentthat the applicant did not in fact draft any claim so as to literallyencompass any particular implementation, and to the extent otherwiseapplicable, the applicant should not be understood to have in any wayintended to or actually relinquished such coverage as the applicantsimply may not have been able to anticipate all eventualities: oneskilled in the art, should not be reasonably expected to have drafted aclaim that would have literally encompassed such alternativeimplementations.

Further, the use of the transitional phrase “comprising” is used tomaintain the “open-end” claims herein, according to traditional claiminterpretation. Thus, unless the context requires otherwise, it shouldbe understood that the term “compromise” or variations such as“comprises” or “comprising,” are intended to imply the inclusion of astated element or step or group of elements or steps but not theexclusion of any other element or step or group of elements or steps.Such terms should be interpreted in their most expansive forms so as toafford the applicant the broadest coverage legally permissible.

We claim:
 1. A method of generating electrical power, the methodcomprising: providing fuel pellets (600) in a rotatable reactor (509)containment insert (1000); controlling an addition of pressurized liquidinto the containment insert; rotating at least the reactor during thepressurized liquid feed addition; generating hydrogen by the hydrolysisof fuel pellets in the reactor; providing hydrogen via fluidcommunication to the anode side of an open cathode PEM fuel cell stack;and, whereby said fuel cell stack generates electricity.
 2. The methodof claim 1 wherein the liquid contains between 100%, and about 80%,water by volume.
 3. The method of claim 1 wherein the pressurized liquidaddition step comprises feeding liquid from a fluid container (506) at afirst flow rate during start-up of the fuel cell stack and reducing theflow rate of the liquid from the fluid container to a rate that is belowthe first flow rate during normal operation of the fuel cell stack. 4.The method of claim 1 further comprising atomizing, with an atomizer, atleast a portion of the pressurized liquid before it reaches the fuelpellets.
 5. The method of claim 1 wherein the fuel pellets compriselithium aluminum hydride.
 6. The method of claim 1 wherein the fuelpellets comprise an admixture of lithium aluminum hydride and anadditive comprising at least one of AlCl₃, MgCl₂, BeCl₂, CuCl₂, LiCl,NaCl, and KCl.
 7. The method of claim 6 wherein the amount of additivein the admixture is <65 wt.-%.
 8. The method of claim 4 wherein theatomizer is an ultrasonic mist generator.
 9. The method of claim 1further comprising turbidity fixtures (602) on an interior surface (510)of the reactor; and whereby turbidity of the fuel pellets is increasedduring rotation of the containment insert as opposed to what occurs witha smooth interior.
 10. The method of claim 1 further comprising at leastone stirring element (604) on at least one of a distal end (530) andproximal end (520) an interior surface (510) of the reactor; and wherebyturbidity of the fuel pellets is increased during movement or rotationof the containment insert as opposed to what occurs with a smoothinterior.
 11. The method of claim 10 wherein the rotation of thecontainment insert is via motor and (514).
 12. The method of claim 1wherein the fuel pellets are between about 4 mm and about 15 mm indiameter.
 13. The method of claim 1 further comprising routing thehydrogen to the anode side of the fuel cell stack at a rate that isexcess of that required by the fuel cell stack for producing poweryielding a recirculation hydrogen stream; enriching the recirculationhydrogen exiting the anode with water; and routing the water-enrichedrecirculation stream to the rotatable reactor.
 14. The method of claim13 wherein the enriching further step comprises: condensing water from acathode air exhaust; converting the condensed water to a mist comprisinga plurality of water droplets using an atomizer; and entraining thewater mist in the recirculation hydrogen stream.
 15. The method of claim13 wherein the enriching step comprises splitting the recirculationhydrogen stream into a first recirculation stream and a secondrecirculation stream using a 3-way valve and routing the firstrecirculation stream to a humidifier and the second recirculation streamdirectly to the reactor bypassing a humidifier.
 16. The method of claim1 wherein the fuel cell stack is a dosed cathode PEM fuel cell stackcomprising a plurality of fuel cells, each cell having an anode side anda cathode side that enables operation of the cathode side at a pressureabove ambient pressure.
 17. The method of claim 16 wherein reactant airto the cathode side of the fuel cell stack is separately provided fromcoolant air to the fuel cell stack.